Step off the Docklands Light Railway at Cutty Sark and walk beyond that tea clipper and the naval college nearby, its cleaved structure once housing the only nuclear reactor within the limits of London. While dodging mudlarks and tourists, strain your ears for the chimes of the Borough Hall clock (time was invented nearby, up the hill at the observatory) then you’ll come to a turquoise dome building staring at its twin on the north riverbank.

This is the Greenwich foot tunnel and I am always astonished at how many lifelong Londoners are unaware of its existence. Being one of only two foot tunnels underneath the Thames currently in use (its centennial twin is in Woolwich) should lend it some magnitude. Yet most people I introduce to it are surprised. At time of writing, I’ve taken three dates to the tunnels (admittedly its damp interior is hardly romantic, though I do hope they found it fascinating) and each was completely unaware that it was there, much less that it is open twenty four-seven and regularly used by commuters from the Isle of Dogs.

Alex via Flickr

I have an affinity for the pokey places in London, atypical landmarks that you might just walk past. My best example is the commemorative plaque to the old Texan embassy near St James’s Park. Tucked into an alleyway between the Kingsman Tailors and Dunhill Tobacco shop, it is easy to miss. However, its position cements a decade of an independent republic of Texas, ten years of which most of us on this side of the Atlantic are unaware.

The Greenwich foot tunnel is no less intriguing. If you continue your exploration of the tunnel from where we left off at the base of the Cutty Sark, you will enter the brick building at whatever time of day you choose. Canary Wharf slips out of view as like many tourists in the capital, you go underground. Your options then are to take the wood panelled lift or the spiral stairs, which are far less interesting and have much less graffiti. For those collecting the footsteps of London’s monuments, the descent has a hundred of them.

The tunnel is the brainchild of the Fenian MP for Woolwich, Will Crooks, whose Punch parody portrait you may find in the men’s bathroom of The Trafalgar pub, at the opposite end of the Naval College. Crooks was born in Poplar, on the other side of the river, and spent most of his life working in the docks and fighting to improve the area for the other labourers who called it home. At the end of the nineteenth century, most workers travelling from the south might have their ferry commute delayed by fog. As well as campaigning for the two foot bridges under the Thames, he advocated for the Blackwall Tunnel (in light of the regular crashes and traffic jams, maybe he should have specified that it be wider) and for Island Gardens, the park which the northern end of the tunnel opens onto.

erroltookaphoto via Flickr

At the lift’s nadir, the doors will slide open and you will be able to see for yourself, the white tiled walls and concrete slabs stretching off out of sight, hidden by the parabolic tunnel’s path. As you travel, you’ll be subjected to minor hazards; drips from the leaking ceilings (the 2011 refurbishments were to repair the worst of these) and prohibited cyclists who seemingly without fail choose to mount their pushbikes anyway and whizz along the subterranean track. Who can blame them? When else would you have the opportunity to cycle under a river in London?

The tunnel is a monument captured in time. Its concrete and cast-iron ring ribbed structure is largely unchanged from when it was originally constructed in 1899. Bombs disturbed the northern side during the Blitz; you can see this steel stented segment towards the distal portion of the tunnel. When the bombs fell (nearly one and a half thousand of them on Greenwich), not then having a convenient underground station to shelter in, many families chose the tunnels. Imagine the combined terror of explosives and the ensuing deluge which might have occurred should the integrity of the reinforced tunnel have been compromised. Let that send a shiver up your back when you feel a drip of damp on your collar.

Jason via Flickr

This timelessness has led towards more esoteric conjecture surrounding the foot tunnels. As part of a catalogue of mysterious portals in London, bloggers have described an anomaly in time occurring down in both tunnels. Workers go down and hours pass, though when they surface it has only been minutes. They radio for additional construction materials, finding they’ve immediately been delivered. If you do delve into the tunnel, check your watch at both ends.

This is not the only strange tale associated with the tunnels. As with all locales bearing an abundance of history, there is the tendency to dredge ghost stories. Some walking the tunnels have claimed to see a Victorian couple passing arm in arm; odd, given that the tunnel only opened a year after Queen Victoria’s death. More commonly reported are echoing footsteps and chatter approaching from the far end. These disembodied sounds disappear at the low point in the path; where one can see that one is alone throughout the tunnel’s twelve hundred foot length.

At the other end of the tunnel, one climbs the shaft. Fewer steps this time, only eighty seven. As you enter squinting into the sunlight, you can sit by the riverbank and admire the breadth of the river you’ve just navigated. Try to imagine the pensioners at Greenwich hospital straining their eyes into a borrowed telescope to watch the regular hangings of pirates which occurred at the spot on which you now stand. The Greenwich Tunnel is a marvel of Victorian and Edwardian engineering. Now that you’ve ticked that box, you’re free to stroll through Millwall to Canary Wharf, take the train tunnel home or pitch your legs back the way you came.

Dmitry Djouce via Flickr

Cover image courtesy of Photographing London via Flickr